The present invention relates to an improved silicon steel core for transformers or choke coils and particularly to a silicon steel core that provides a desired induction for transformers or choke coils and improves magnetic saturated functions.
Various types of choke coils are widely used in electric products of different functions. They also play a very important role in the power supply of the electric products. The choke coils can increase energy utilization efficiency and reduce power supply interference in the electric systems. In addition to improving service life of the electric devices, they also can protect environments. Thus they are simple and indispensable elements in many electric products.
The general transformers or choke coils have silicon steel sheet cores made of a first silicon steel sheet core 3 and a second silicon steel sheet core 4 formed in E and I shapes (as shown in FIGS. 1 and 2). When the first and the second silicon steel sheet cores 3 and 4 are coupled, their magnetic flux sections correspond to each other. Moreover, there is an insulated spacer 5 located between the central magnetic flux sections 31 and 41 of the first and the second silicon steel sheet cores 3 and 4. The thickness of the spacer 5 may adjust the gap of the magnetic flux sections 32, 32xe2x80x2, 42 and 42xe2x80x2 on two flanks of the first and the second silicon steel sheet cores 3 and 4. As the size of the gap determines the inductance output by the transformers or choke coils, when the gap is small, the magnetic resistance of the line of magnetic force running on the magnetic path decreases, the electric induction being formed is greater, thus the choke coil has sufficient electric induction even in a small load condition. However, when the load is high, the magnetic core is easy to become saturated. When the gap is larger, the magnetic resistance of the line of magnetic force running on the magnetic path increases, the electric induction being formed is smaller. While it is not easily saturated in the high load condition, it also cannot achieve the required electric induction in the small load condition unless the number of copper coils or silicon steel sheets increases.
The gaps on the two flanks of the first and the second silicon steel sheet cores 3 and 4 are equal. As the gap determines the saturated current and induction, in the event that the number of copper coils and silicon steel sheets cannot be increased due to space constraint or cost reason, to raise the induction to a desired level and to increase the saturated current of the transformers or choke coils at the same time become very difficult.
In addition, the harmonic test (European regulations) usually has an upper limit value (depending on the required power set by electric devices) and a lower limit value (minimum 75W according to the present requirement, and must reach 50W in 2004). For the transformer or choke coil made of the silicon steel sheet sets of an equal gap discussed above to achieve the minimum limit value, the electric induction must increase. Then the gap of the silicon steel sheets must be reduced. As a result, the magnetic core of the transformer or choke coil is easy to become saturated when the electric device is in the high load condition. And the device cannot pass the harmonic test in the heavy load condition. To pass the harmonic test, the number of copper coils or silicon steel sheets has to be increased to boost the induction. This causes fabrication difficulty and rising cost.
Therefore the primary object of the invention is to resolve the aforesaid disadvantages. The invention provides a gap design for the first and the second silicon steel sheets that has gaps of different intervals so that they can supply induction required in the low load condition and also has a larger gap to meet the requirements in the high load condition.
Another object of the invention is to reduce fabrication cost.
Yet another object of the invention is to conform to the harmonic test requirements.
In order to achieve the foregoing objects, the improved silicon steel core of the invention includes at least one silicon steel sheet core which has at least two sets of silicon steel sheets. Each set of silicon steel sheets has a magnetic flux section of a different length. When the two sets of corresponding silicon steel sheets are coupled, every magnetic flux section forms at least two gaps of different intervals to provide outputs of different power supply (watts).
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.